Tried my set up today during a PT. Protein Bar with my standby options of 5 hour energy shot and or a nicotine lozenge. Ate the bar and went with the lozenge, did not feel I needed the caffeine. The snack and nicotine gave me a nice little boost, and kept me level headed for the remain two multiple choice sections.
If anything, take a PT or 2 between the now and the test. See if the snack you set aside gives you enough energy, makes you feel crummy, etc. I stand by, "better to have it and not need it, then not have it and need it." So, consider bringing a few options, some of which you may not consume.